1. Field of the Invention
The present invention relates to a tire position detecting device for detecting the position of a tire, and to a wheel alignment adjusting device for adjustment the alignment of wheels of a vehicle.
2. Description of the Related Art
Generally, wheels of a vehicle are provided with a camber angle for ensuring traveling stability of the vehicle, and are provided with a toe angle for preventing irregular wear caused by the provision of the camber angle.
Or, conversely, a toe angle is provided in order to balance the forces generated at the front tires and at the rear tires of the vehicle so as to ensure travelling stability of the vehicle, and the toe angle and the camber angle are combined so as to carry out adjustment for improving the traveling stability of the vehicle and minimizing the irregular wear of the tire under limiting conditions such as the structural dimensions of the vehicle and the like.
Accordingly, in order to improve the traveling stability and irregular wear resistance of the tire when the vehicle is traveling, it is important to adjust the toe angle and the camber angle, which are positional angles (wheel angles) applied to each wheel.
Adjustment of the toe angle and the camber angle is carried out by using a wheel alignment adjusting device.
When wheel alignment adjustment of a vehicle is to be carried out at a wheel alignment adjusting device, the vehicle is loaded onto the wheel alignment adjusting device from one end of the device, and is stopped at a predetermined position. The wheels are fixed, various measurements are carried out, and wheel alignment adjustment is carried out on the basis of the various measured values.
When various types of measurements are carried out, the center line of the wheel alignment adjusting device and the center line of the vehicle body must correspond with one another.
Thus, conventionally, the positions of the respective wheels have been measured by using a laser (e.g., Japanese Patent Application Laid-Open (JP-A) No. 9-280843, JP-A-9-329433), or by a potentiometer (JP-A-7-35652), or by a dial gauge. When the left and right dimensions differ, it is judged that the center line of the vehicle body does not coincide with the center line of the wheel alignment adjusting device. The positions of the loading stands on which the wheels are loaded are adjusted so that the position of the vehicle is corrected.
Conventionally, distance was measured by illuminating a laser onto the side surface of a tire or bringing a member into contact with the side surface of the tire. However, because there are indentations on the side surface of the tire and because the tire itself is made of rubber and deforms easily, errors in measurement are great for reasons such as the measured values are different each time measurement is carried out.
In view of the aforementioned, an object of the present invention is to provide a tire position detecting device, which can detect the position of a wheel precisely and with high accuracy, and a wheel alignment adjusting device.
A tire position detecting device of a first aspect of the present invention comprises a wheel-mounted jig which is mounted to a disc wheel of a wheel; and a position measuring device provided at a wheel loading portion on which the wheel is loaded, the position measuring device including: a connecting member, one end of the connecting member being pulled out from a predetermined position of the distance measuring device and being connected to a predetermined position of the wheel-mounted jig; and a sensor which measures a pulled out amount of the connecting member.
In the tire position detecting device of the first aspect, the wheel-mounted jig is mounted to the disc wheel of the wheel. The disc wheel is a substantially highly rigid body (i.e., is made of metal, and deforms less easily than the rubber forming the tire). Thus, the positional relationship between the wheel-mounted jig and the disc wheel when the wheel-mounted jig is mounted to the disc wheel is stable.
When the connecting member of the distance measuring device is pulled out and a predetermined position of the distance measuring device (a predetermined position of the wheel loading portion) and a predetermined position of the wheel-mounted jig are connected, the sensor measures the pulled out amount of the connecting member.
The wheel-mounted jig is mounted to a region of the wheel which is difficult to deform, namely, a stable region (the disc wheel). Thus, the predetermined position of the wheel-mounted jig is also a stable region. The sensor can accurately and precisely measure the pulled out amount of the connecting member which connects the predetermined position of the distance measuring device (the predetermined position of the wheel loading portion) and the predetermined position of the wheel-mounted jig.
In a second aspect of the present invention, in the tire position detecting device of the first aspect, the predetermined position of the wheel-mounted jig is on an axis of the wheel.
A unique point which is easy to specify does not always exist on the outer periphery of all disc wheels. However, the point at which the axis of the wheel and the disc wheel intersect, i.e., the central portion of the disc wheel, is a unique point only one of which exists on the disc wheel. Thus, this position is easy to specify, and is suitable as a reference for measurement.
In a third aspect of the present invention, in the tire position detecting device of either the first or second aspect, the connecting member is a wire.
Because the wire can be bent freely, the wire can be easily and compactly accommodated within the distance measuring device.
In a fourth aspect of the present invention, in the tire position detecting device of any of the first through third aspects, the position measuring device further includes: a pull out opening from which the wire is pulled out; an anchoring portion on which another end portion of the wire is anchored; at least one running pulley, a portion of the wire between the pull out opening and the anchoring portion being trained around the running pulley; and an urging device which urges the running pulley in one direction such that tensile force is applied to the wire.
In the tire position detecting device of the fourth aspect, when the wire is pulled out from the pull out opening, if one running pulley is provided, the running pulley is moved by an amount which is one-half of the pulled out amount of the wire. Accordingly, when the wire is accommodated within a fixed predetermined length of the distance measuring devices the amount of the wire which can be accommodated can be increased as compared to a case in which no running pulley is used. Also, flexible arrangement of the wire is possible.
Further, the running pulley is urged in one direction by the urging means. Thus, while the wire is pulled out from the pull out opening to the predetermined position of the wheel-mounted jig, the wire does not go slack, and the pulled out amount of the wire can be measured precisely and accurately.
By increasing the number of running pulleys even more, the amount of the wire which can be accommodated over a given length can be increased even more.
In a fifth aspect of the present invention, in the tire position detecting device of any of the first through fourth aspects, the sensor is a rotary encoder having a rotational shaft around which the wire is trained and which rotates due to movement of the wire, the rotary encoder outputting a signal corresponding to an amount of movement of the wire.
In the tire position detecting device of the fifth aspect, when the wire is pulled out, the rotary shaft of the rotary encoder is rotated, and the rotary encoder outputs a signal corresponding to the moved amount (the pulled out amount) of the wire. The moved amount of the wire can be known on the basis of this signal.
A sixth aspect of the present invention is a wheel alignment adjusting device comprising: (A) a wheel-mounted jig which is mounted to a disc wheel of a wheel; (B) a position measuring device provided at a wheel loading portion on which the wheel is loaded, the position measuring device including: (i) a connecting member, one end of the connecting member being pulled out from a predetermined position of the distance measuring device and being connected to a predetermined position of the wheel-mounted jig; and (ii) a sensor which measures a pulled out amount of the connecting member; (C) a moving device which moves the wheel loading portion in a horizontal direction; (D) a rotation device provided at the wheel loading portion and rotating the wheel; and (E) a force sensor connected to the wheel loading portion and measuring a force which is applied to the wheel loading portion.
In the wheel alignment adjusting device of the sixth aspect, the positions of the wheels loaded on the wheel loading portions can be measured by the respective tire position detecting devices.
The relationship between the central line of the vehicle body and the central line of the wheel alignment adjusting device can be known by measuring the positions of the respective wheels. At least one of the wheel loading portions is moved by at least one of the moving means such that the central line of the vehicle body and the central line of the wheel alignment adjusting device coincide with one another. The position of the vehicle body can thereby be corrected.
In a seventh aspect of the present invention, the wheel alignment adjusting device of the sixth aspect further comprises a control means for controlling the moving device to move the wheel loading portion on which a vehicle left front wheel is loaded and the wheel loading portion on which a vehicle right front wheel is loaded such that a pulled out amount of the connecting member measured by the distance measuring device corresponding to the vehicle right front wheel and a pulled out amount of the connecting member measured by the distance measuring device corresponding to the vehicle left front wheel are the same, and for controlling the moving device to move the wheel loading portion on which a vehicle left rear wheel is loaded and the wheel loading portion on which a vehicle right rear wheel is loaded such that a pulled out amount of the connecting member measured by the distance measuring device corresponding to the vehicle right rear wheel and a pulled out amount of the connecting member measured by the distance measured device corresponding to the vehicle left rear wheel are the same.
In the wheel alignment adjusting device of the seventh aspect, the control device controls the moving means to move the wheel loading portions on which the left and right front wheels are loaded such that a pulled out amount of the connecting member measured by the distance measuring device corresponding to the vehicle right front wheel and a pulled out amount of the connecting member measured by the distance measuring device corresponding to the vehicle left front wheel are the same. The control device controls the moving means to move the wheel loading portions on which the left and right rear wheels are loaded such that a pulled out amount of the connecting member measured by the distance measuring device corresponding to the vehicle right rear wheel and a pulled out amount of the connecting member measured by the distance measuring device corresponding to the vehicle left rear wheel are the same. In this way, the central line of the vehicle body and the central line of the wheel alignment adjusting device can automatically be made to correspond to one another.
In an eighth aspect of the present invention, in the fourth aspect, the pull out opening can be moved onto an axis of the wheel.
In a ninth aspect of the present invention, in the first aspect, the position measuring device has a first case and a second case, and one longitudinal direction end portion of the first case is fixed to a predetermined position of the wheel loading portion such that the first case is rotatable about the one longitudinal end portion, and the first case supports the second case such that the second case is movable in a longitudinal direction of the first case.
In a tenth aspect of the present invention, in the tire position detecting device of the ninth aspect, the second case includes: a pull out opening from which a wire is pulled out; an anchoring portion on which another end portion of the wire is anchored; at least one running pulley, a portion of the wire between the pull out opening and the anchoring portion being trained around the running pulley; and an urging device which urges the running pulley in one direction such that tensile force is applied to the wire.